Vehicle subsystem monitors

ABSTRACT

A multiple error detection system utilizing light-emitting diodes to form a character representation in response to a given error signal input.

United States Patent LIN/N6 //6 WEAR SE N501? PARK/N6 V BRAKE SENSORSPLIT SYSTEM sE/vsoR 12 [56] References Cited UNITED STATES PATENTS3,541,550 11/1970 i-lamre 340/52 X 3,5 I 2,405 5/1970 Schlicher 340/415X OTHER REFERENCES IBM Technical Disclosure Bulletin; R. W. Landauer;Electroluminescent Display; April I966; Vol. 8, No. ll; Pages 1569 andI570.

I Primary ExaminerAlvin H. Waring Attorneys-C. F. Arens and Flame,Arens, Hartz, Smith and Thompson ABSTRACT: A multiple error detectionsystem utilizing lightemitting diodes to form a character representationin response to a given error signal input.

BRAKING SYSTEM V/SUA L PARAME T E5 PRESENM T/ON LIA/MIG WEAR I SPLITsvsreu I MRK/NG BRAKE S/GNAL CONDITION/N6 ADAPT/ VE BRA K E MALFUA/CT/ONLIGHT EMITTING DIODES ADAPTIVE BRAKING FLU/D LEVEL SENSOR VA CUUM SENSORVEHICLE STARTER SWITCH ENCODING LOG/C BRA/(E SYSTEM PERFORMANCE FIBER0PT/C FLU/D LEVEL ENG/NE VACUUM I SELF TEST 0N START MON TOR PATENTEUnEc71971 3626367 SHEET 3 BF 3 12 VOLTS fig /60 INVEN'lURS DONALD m HOW/4R0I i 5 s BY DEWEY m EPPLEY /62 IOM,QW, M

1; Q (ATTORNEYS VEHICLE SUBSYSTEM MONITORS BACKGROUND OF THE INVENTIONindication of the performance of the automobile. The present vehiclesplit-braking system includes a warning light which will indicate a lossof front or rear brake pressure during a brake application. A warninglight may be latched on some model vehicles while on others the warninglight is energized only on a transient basis. Self-test of the above maybe auto matic when the vehicle is started, or it may be checked by asecond function such as a parking brake.

Monitoring of other brake parameters is being considered today. Theseparameters include master cylinder fluid level, lining wear, andadaptive braking control performance. With this increased demand itbecomes apparent that a multiplicity of indicators will be required todetect all functions. Add to this increased indication needs for powerplant, adaptive steering, adaptive speed control, and emission controldevices, and the instrument panel will become a maze of indicators whichwould distract rather than enhance the original purpose.

What is needed is a monitor that is simple, yet will convey an increasedamount of information in a concise and orderly fashion to the operatorof the automobile. The monitor should not only tell whether the systemis in a go" or no-go type condition, but it also should tell theoperator of the vehicle which subsystem is in a go" or no-go" condition.This gives a diagnostic capability to the operator with a consequentialpotential savings in maintenance cost. For example, in modern vehiclebraking subsystems the operator should know if the parking brake is on,if the master cylinder fluid level is low, if the front or rear brakepressure is low, if the brake lining is worn, if the adaptive brakingcontrol is malfunctioning, or if the vacuum is lost in the power brakeboost. Also, a self-check of the circuit should be provided so that theoperator will know if the circuit itself is functioning properly.

The monitoring of these many different functions becomes possible withrecent developments in integrated circuits, lightemitting diodes, andfiber optics. Current technological advances in the integrated circuitsfield permits several hundred active elements to be combined on a singlechip, but the cost per function of an integrated circuit is limited on asmall quantity basis. However, economic feasibility of custom circuitsin production quantities can be predicted in the automotive industry.Light-emitting diodes have just recently become available on thecommercial market. On a mass production basis, the lighbemitting diodeswill be economically feasible in automotive industry. If light emittedfrom the light-emitting diodes does not give the desired characterrepresentation, the use of fiber optic techniques can reshape the lightemitted from the diode to form the given character representationdesired.

SUMMARY OF THE INVENTION Accordingly, it is an object of this inventionto utilize a single monitor for a number of error inputs.

It is a further object of this invention to utilize a plurality ofsensors and a plurality of light-emitting diodes that are interconnectedin such a manner that a different visual character representation outputis formed for an error signal from a given sensor.

It is a further object of this invention to provide signal conditioningto the sensor outputs whereby the sensor outputs can be accepted bydigital logic which controls the previously arranged light-emittingdiodes to form a different lighted alphabetic character for each errordetected by the sensors.

These and other objects of the invention are accomplished by changingthe sensor outputs to a given voltage level. This voltage level is fedinto a NOR gate which controls a given segment of the characterrepresentation. By selecting the proper combination of NOR gates, agiven character representation can be formed by the illumination of itsdifferent segments. Each segment may be formed by one, or a combination,of light-emitting diodes depending on the amount of illumination whichis needed. If better clarity in the character representation is desired,a fiber optic display may be utilized.

DESCRIPTION OF THE DRAWINGS The invention herein disclosed will be morefully understood when taken together with the accompanying drawings inwhich:

FIG. I is an illustrative block diagram that shows the normal signalflow in the error detection system;

FIG. 2 is a diagrammatic circuit diagram of the error detection systemshown in FIG. 1;

FIG. 3 is an illustrative character representation that can be formed bythe outputs of FIG. 2;

FIG. 4 is a circuit diagram of the preferred embodiment shown in FIG. 1;and

FIG. 5 is a circuit diagram of a voltage regulator operated from theautomobile battery for supplying regulated voltage to the errordetection system.

DESCRIPTION OF THE PREFERRED EMBODIMENTS With continued reference to theaccompanying figures initial attention is directed to FIG. 1. Aplurality of sensors, represented generally by reference numeral 10,detect an outof-tolerance condition in a subcomponent of a brakingsystem. The output of the sensors 10, if necessary, is changed to agiven voltage level by signal conditioner I2. This voltage level is fedinto encoding logic 14 which controls a number of lightemitting diodes16. These light-emitting diodes 16 are arranged in such a manner to forma character representation, such as an alphabetic or numeric readout. Togive a better visual indication of the character representation, a fiberoptic display I30 may be used.

By referring to the logic diagram as shown in FIG. 2, one can betterunderstand the forming of the character representation. The output ofthe sensors 18, 20, 22, 24, 26, and 28, after being converted to a givenvoltage level by the respective signal conditioner 30, 32, 34, 36, 38,and 40, is represented by the letters L, P, S, A, F, and B,respectively. These outputs L, P, S, F, and B, are connected to NORgates 42, 44, 46, 48, 50, 52 and 54 contained in encoding logic 14. Thenormal output from the signal conditioner I2 is zero volts. A positivevoltage indicates an out-of-tolerance condition. With no out-oftolerancecondition all of the inputs on the NOR gates will be zero. If there isno input on a NOR gate, the output of the NOR gate should be at apositive voltage level. The output of the NOR gates 42, 44, 46, 48, 50,52, or 54, represented generally by numerals 55, is connected to oneside of the lightemitting diodes 56, 58, 60, 62, 64, 66, or 68,respectively, represented generally by numeral 69. The other side of thelight-emitting diodes 69 is connected to a voltage source V,. With apositive voltage approximately equal to V, on the output of a NOR gateand the voltage source V, connected to the other side of thelight-emitting diode, there will be no conduction through thelight-emitting diode because both sides are at approximately the samevoltage potential.

However, when a voltage is applied to the input of the NOR gate by oneof the sensor devices 18, 20, 22, 24, 26, or 28, the output of the NORgate will go from a positive to a zero level causing the light-emittingdiode to be connected between the voltage source V, and a zero potentialwhereupon current conduction will begin. During conduction thelight-emitting diode illuminates. The illumination from thelight-emitting diode can be used to form a segment of a characterrepresentation. As can be seen from FIG. 2, each NOR gate andlightemitting diode combination is used to form one segment of aseven-segment character. Segment a can be formed from an input of A, B,F, P, or S; Segment b," an input of A, B, or P;

segment C," an input of A, B, or S; segment d," an input of B, L, or S;segment e, an input of A, B, F, L, or 1; Segment f,an input of A, B, F,L, P, or S; Segment g," an input of A, B, F, P, or S. The arrangement ofthese separate segments is shown in FIG. 3.

Before following each sensor output through the encoding logic 14, abrief explanation of the light-emitting diode is in order. As forwardbias is applied to the diode, electrons are injected into the P-layerfrom the N-layer and, conversely, holes are injected into N-layer fromthe P-layer. The near surface combinations in a light-emitting dioderesults in a photon emission or visible light. The color of the light isa function of the bandgap energy (electron volts) as controlled by thedoping and purity of the materials. A typical light-emitting diode is aphosphide doped gallium arsenide diode which can produce ZOO-footlamberts at milliamperes of forward current. An example of this type oflight-emitting diode can be found in the technical data sheet ofMonsanto, Alpha Numeric Display, MAN-l. Another example of prearrangedsegments to form given character representations can be found in thetechnical data sheet of Monsanto, Visible Solid State Light Source,MV-lOB.

Taking each sensor individually, a voltage V, is applied through theresistor 70 to lining probes 72 and through another resistor 74 toground to provide the lining wear sensor 18 with a source of power. Theoutput of the lining wear sensor 18 is inverted through inverter 76 togive output L. Output L is fed into the NOR gates that control Segments,d, e, and f, thereby forming the visual representation of the letter L.

The parking brake sensor 20 controls a normally open contact 76 with oneside 78 of the normally open contact 76 connected to ground. The otherside 80 of the normally open contact 76 is connected through a resistor82 to the voltage source V,. The output of the parking brake sensor 20is normally at a positive voltage until an error is sensed whereby thenormally open contact 78 is closed and the voltage drops to zero. Theoutput of the parking brake sensor 20 is fed through an inverter 84 inthe signal conditioner 32 to form the output voltage P. P is fed intothe NOR gate and light-emitting diode combination that makes Segments[2," a," e," f," and g,38 thereby forming the visual presentation of theletter P.

A split system sensor 22 operates a normally closed switch 86 when thereis an unbalanced condition between the front and rear brakes. One side88 of the normally closed switch 86 is connected to ground and the otherside 90 through a resistor 92 to the voltage source V Upon brakeapplication if there is a pressure differential between the front andrear brakes, the contact 86 will momentarily open thereby supplying apositive voltage output. This positive voltage output is processed inthe signal conditioner 34 by feeding into an inverter 94 through aresistor 96 and diode 91. The signal conditioner 34, which also performsa latching function, uses an R-C filter time constant consisting ofresistor 96 and capacitor 98 connected between the split system sensor22 and the input to inverter 94. Capacitor 95 sets inverter 97 to aninitial conducting state with a zero voltage output S when voltage V, isapplied and sensor switch 22 is closed. The output of inverter 94 is ata positive voltage level. if the sensor 22 opens for a period exceedingthe R-C time constant (96 and 98), inverter 94 is switched on, whichpulls down the output ofinverter 94 to zero. Consequently, inverter 97stops conducting which raises the output 8 to a positive voltage level.The output S is fed back through diode 93 to hold the inverter 94 in theconducting state or latched ON. The diode 91 prevents breakdown of thelatching function if sensor 22 later closes. Therefore, for a momentaryopening of the normally closed switch a steady state voltage output Scan be realized. The voltage S is connected to the NOR gates andlight-emitting diodes that control Segments a, c," and g, therebyforming the visual presentation of the letter S.

An adaptive brake malfunction 24 will remove the voltage V, from thecross resistor 100 and 102. With removal ofthis voltage V the input toinverter 104 becomes zero thereby giving a positive voltage output of A.Voltage A controls NOR gate and light-emitter diode combinations thatform Segments a,"b," c," e," f," and g," thereby forming the visualpresentation of the letter A.

The fluid sensor 26 operates at normally closed contact 106 with oneside 108 of the normally closed contact connected to ground, and theother side 1 10 of normally closed contact 106 being connected through aresistor 112 to a positive voltage source V,. No signal conditioningbeing necessary, the output of the fluid level sensor 26 feeds directlyinto the encoder 14 and is represented by the letter F. F feeds into theNOR gatelight emitter diode combinations that form the Segments a," f,"and g, thereby forming a visual presentation of the letter F.

The vacuum loss sensor 28 controls a normally closed contact 114. Oneside 116 of the normally closed contact 114 is connected to ground. Theother side 118 of the normally closed contact 114 is connected through aresistor 120 to a voltage source V,. The output of the vacuum losssensor 28 could be fed directly into the encoding logic 14. However, toprovide an auxiliary test means 124, it is connected to the encodinglogic 14 through a diode 122. The test means 124 which is connected tothe encoding logic side of the diode 122 if formed by a connection fromthe starter through a resistor 126 and a diode 128 to form the voltageB. Voltage B, which also represents a vacuum loss, controls the NORgate-light emitting diode combinations of Segments a," b, c, "d," e,"f," and g," thereby forming the visual presentation of the letter B,Because letter B illuminates all of the segments, it can also be used asthe test means 124 to determine if all lightemitting diodes 69 arefunctioning properly.

The interconnections for the encoding logic 14 is determined by writinga truth table which relates the sensor output as a function of thedesired alphabetic character as shown below:

Segment identification d e f Sensor and alphabetic character a b Liningwear L" 1 Adaptive braking A. Parking brake I Fluid level F r. Splitsystem S".

PowerboostH'B" o Self test If a good character representation cannot beobtained directly from the light-emitting diodes 69, the individualSegments 56, 58, 60, 62, 64, 66, and 68 can be reshaped by the use offiber optic techniques depending upon the size of the characterrepresentation desired. Fiber optics can greatly reduce the number oflight-emitting diodes 69 required and reduce the encoded circuit 14complexity. An example of the fiber optic display 130 is shown in FIG.1.

The preferred circuit diagram for FIG. 1 is shown in H0. 4. Note thatall of the inverters 76, 84, 94, and 104, as described in conjunctionwith FIG. 2, are identical. They each have an input resistor 132connected to the base 136 of the transistor 134. The emitter 138 of thetransistor 134 is connected to ground. The collector 140 of thetransistor 138, which is the output, connects through a resistor 142 tothe voltage source V,,.

Each of the NOR gates 42, 44, 46, 48, 50, 52, and 54, as described inconjunction with FIG. 2, have identical configu rations even though thenumber ofinput diodes 144, 146, 148, 150, 152, 154, and 156,respectively, may vary. Each of the NOR gates contain an inverter asdescribed in the previous paragraph, Like numerals will apply tocomparable component parts of the inverters in the signal conditioner 12or the encoding logic 14. The inverters consist of a transistor 134, thebase 136 of which is connected to the input resistor 132. The emitter138 is connected to ground. The collector side 140 of the transistor134, which is the output of the NOR gate, connects to the light-emittingdiodes 69. Also connected to the collector 140 of the transistor 134 isa resistor 142 the other side of which connects to the voltage sourceV,,. Because a single light-emitting diode may not provide a segment ofsufficient length, two lighting diodes work as shown in series. By usingtwo light-emitting diodes (their respective numeral plus X or Y) inseries, a segment of sufficient length and illumination can be obtained.it is realized that any number of lightemitting diodes can be used toform a particular segment. As technology in this field develops, it maybe possible for one light-emitting diode to provide sufficientillumination to give the size of segment or character desired.

The voltage source V,which is used to drive the signal conditioning l2and encoder logic 14, as well as the light-emitting diodes 69, isregulated as shown in H0. 5. The regulator 158 consists of a resistor160 in series with the zener diode 162, the resistor side beingconnected to the battery voltage and the zener diode side beingconnected to ground, wherein regulated voltage output V, can be obtainedbetween the resistor 160 and the zener diode 162. In a laboratory model,a voltage source V, of 3.6 volts was used.

in the laboratory breadboard model, resistor-transistor logic plusdiscrete diodes were used. However, diode-transistor logic could havebeen incorporated at a slight increase in complexity. On the laboratorymodel, no attempt was made to miniaturize the circuit board. inproduction quantities the entire circuit, including the light-emittingdiodes, could be fabricated on a single monolithic hybrid chip which ispackaged to mount directly on the automobile dash. Conversion of thisdevice to a custom package incorporating integrated circuits,light-emitting diodes, resistors, regular diodes, and, if necessary,fiber optics is economically feasible in production quantities. State ofthe art semiconductors presently considers a theoretical packing densityof 3.5 million components per square inch on the chip. Externalmechanical connections drastically reduce this value. However, sincecircuitry for this unit requires less than 100 individual components, awafer dimension of 50 by 100 mills is more than adequate.

Application of the above philosophy to other vehicle subsystems becomesreadily apparent. A single character display module could monitor engineand accessories as noted in table ll.

Fuel Low Air conditioning Malfunction l:

Seat belts Unlatched L The vehicles of the future will probably containmany applications of integrated circuits and light-emitting diodes inthe display system. This adds, not only to the indications available,but also to the comfort of the operator with essentially no increase incost.

What is claimed is:

1. A vehicle malfunction indicator system comprising:

a plurality of sensors, each of said sensors being adapted to detect amalfunction in a component of the vehicle;

a plurality of light-emitting diodes arranged in segments of a matrix,said segments being arranged to form visual character representationswhen different combinations of the segments are activated; and

gating means for each of said segments, each of said gating means havingan output terminal connected to its corresponding segment and aplurality of inputs, each input of each gating means being connected tothe output of one of said sensors, the output of each of said sensorsbeing connected to the input of more than one of said gating means, theoutput of each of said sensors being connected to a differentcombination of gating means than the output of any other sensor;

each of said gating means activating its corresponding segment when anyof the sensors connected to any of its input terminals produces anoutput signal.

2. The invention of claim I:

each of said gating means being a NOR gate, whereby a positive voltagelevel is maintained in the output of the latter in the absence of asignal to the input of a corresponding NOR gate;

said light-emitting diodes being connected between the output of thecorresponding NOR gate and a voltage source.

3. The automotive malfunction detection system, as recited in claim 1,still further comprising a fiber optic display wherein said characterrepresentations from said lightemitting diodes are visually displayed inalphabetic and numeric form.

4. A brake malfunction indication system, as recited in claim 1, whereinsaid sensors indicate dangerous lining wear, vacuum loss, fluid level inmaster cylinder, adaptive brake malfunction, parking brake on, splitsystem malfunction, and self-test on start, said brake malfunctionindication system further comprising:

a fiber optic display means for giving better visual effects to saidletters indicated by said light-emitting diodes.

1. A vehicle malfunction indicator system comprising: a plurality ofsensors, each of said sensors being adapted to detect a malfunction in acomponent of the vehicle; a plurality of light-emitting diodes arrangedin segments of a matrix, said segments being arranged to form visualcharacter representations when different combinations of the segmentsare activated; and gating means for each of said segments, each of saidgating means having an output terminal connected to its correspondingsegment and a plurality of inputs, each input of each gating means beingconnected to the output of one of said sensors, the output of each ofsaid sensors being connected to the input of more than one of saidgating means, the output of each of said sensors being connected to adifferent combination of gating means than the output of any othersensor; each of said gating means activating its corresponding segmentwhen any of the sensors connected to any of its input terminals producesan output signal.
 2. The invention of claim 1: each of said gating meansbeing a NOR gate, whereby a positive voltage level is maintained in theoutput of the latter in the absence of a signal to the input of acorresponding NOR gate; said light-emitting diodes being connectedbetween the output of the corresponding NOR gate and a voltage source.3. The automotive malfunction detection system, as recited in claim 1,still further comprising a fiber optic display wherein said characterrepresentations from said light-emitting diodes are visually displayedin alphabetic and numeric form.
 4. A brake malfunction indicationsystem, as recited in claim 1, wherein said sensors indicate dangerouslining wear, vacuum loss, fluid level in master cylinder, adaptive brakemalfunction, parking brake ''''on,'''' split system malfunction, andself-test on start, said brake malfunction indication system furthercomprising: a fiber optic display means for giving better visual effectsto said letters indicated by said light-emitting diodes.